Tantalum pentoxide thin films are prepared by oblique angle electron beam evaporation.The influence offlux angle on the surface morphology and microstructure is investigated by scanning electron microscopy(SEM).The Ta_2O_5 thin films are anisotropic with highly orientated nanostructure of slanted columns.The porous microstructure of the as-deposited films results in the decrease of effective refractive index andpacking density with increasing deposition angle.The anisotropic structure results in optical birefringence.The in-plane birefringence increases with the increase of deposition angle and reaches the maximum of0.055 at the deposition angle of 70°.Anisotropic microstructure and critical packing density are the twokey factors to influence the in-plane birefringence.
